. . . it was engineering and careful fabrication.

Roll center: I located the static roll center before I changed the A-arms, plotted it on my AutoCad, then fabricated the upper control arms to make sure it did not change. I also tracked (AutoCad again) the movement of the roll center under a range of body rolls - both with the original and the modified A-arms. I didn't consider the minor differences I saw to be significant.

Scrub radius: Again, I measured it, and kept the relative position of the upper and lower ball joints constant. Scrub radius stayed slightly positive both before and after the modification.

Caster: No change. There was plenty of adjustment.

Static Camber was set at ride height the same with the modified arms as it was with the stock arms. Granted, camber changes as the arms swing, but I plotted that on Autocad also, and found that the difference wasn't significant over the limited travel of a high-performance hot rod suspension setup. The old adage that steering geometry becomes less critical with less motion is still true.

Finally, here's something to consider. In putting something like a MII suspension under a street rod with a different ride height, weight, center of gravity, instant center, power level, weight distribution, and just about any other specification we care to consider, it's kind of a crapshoot to start with unless either the builder or the supplier engineer the application. The relatively minor mods I made caused no difference.

I could take my hands off the wheel at 120, and it cornered like a dream. No shake, no tire wear, no problem.

But I do agree with you that someone buying off the shelf should be careful.

By the way, changing the backspacing WILL change scrub radius - and not in the direction you want to go with a rear wheel drive car.